The present invention relates to a complementary-MOS integrated semiconductor device provided on a single substrate, and more particularly to a complementary-MOS integrated semiconductor device having two different threshold voltage levels.
The complementary-MOS IC and the complementary-MOS LSI have, in general, great advantages in their high switching velocity and their extremely small power dissipation. In the C-MOS IC or C-MOS LSI of the prior art, every channel was constructed to have the same threshold voltage level. When the C-MOS IC or C-MOS LSI were utilized in for an electronic wristwatch or an electronic calculator driven by a low voltage power source such as a cell, the respective channels were so constructed to have a relatively low threshold voltage level.
It was required to include a drive circuit for a display system comprising, for example, light-emitting diodes or a crystal display unit, within a single C-MOS IC or C-MOS LSI. The light-emitting diodes and the liquid crystal display unit are usually driven by a relatively high voltage. When the high voltage is applied to the C-MOS IC or C-MOS LSI having the relatively low threshold voltage level, the elements may be ruptured or the elements consume large amounts of power.